The Validator saves the tags as an array. Now also another information
is added, which slots aren't used currently to spare expensive calls to
realloc. This led to a mere reimplementation of the functions. Tags
can't be deleted by now, but the adding function supports reusing empty
slots. Also the reading functions have to determine, whether a slot can
be read or is empty.
The tests were adjusted, but are buggy, so they should be rewritten in
the future.

Additionaly some annotations for splint were added.

Instead of the trivial structure SH_Error, SH_Status is used. The name
was chosen, because error/status is set independently whether an error
has occurred. Beside the error type, it also contains the associated
errno and an error message. The error message is also printed, when it
is set. Generating error messages with variadic arguments is now also
supported.
There are also macros to check for a set status.

The exception handling was removed for the *_free methods, because they
can't fail predictably during runtime.

Unfortunately the compiler reports, that inside the macro set_status
printf may be called with NULL [printf (NULL)], although, this is
explicitly debarred.

On initialization (of data), the Validator's knowledge is filled with some
common tags. This is of course to be replaced later, by some dynamic handling.